Well, I’ll give it a wing, so here goes.
1:
The big differences I can toss at you right away.
In BJJ you often here “position before submission”
whereas in catch, you could consider the philosophy to be the reverse.
BJJ will often stress attaining a more dominant position and in doing so, opening up more submission opportunities. In contrast, catch wrestling philosophy has to do with being able to attack from any position, hence the great variety of footlocks that its famous for. Even when giving their backs, its not uncommon to see them attempt footlocks (say a figure four toehold) on their opponents hooks rather than escape. In this respect, you’d been more likely to see BJJ fighters doing more guard passing and catch wrestlers attacking the feet.
2:
As far as BJJ favoring the guard- it doesnt, it simply acknowledges that a fight can be won from ones back, and if worked on well enough, this skill can prove to be very usefull. Natrually catch wrestling, having been associated with freestyle, greco, and folkstyle, saw the bottom positions as not being too effective.
In this respect, you’re more likely to see two catch wrestlers fight for top position superiority rather than the BJJ fighters who would play the game you so commonly see in today’s submission wrestling tournaments. Matt Hughes vs Sean Sherk would be a good example of the first, while Ricco Rodriguez vs Antonio Rodrigo Nogueira would be a good example of the BJJ fighters.
3:
Catch wrestling would happen to favor submissions that could be applied without the potential to lose a position. According to this philosophy, submissions such as keylocks and bicep cutters would be much more popular than your standard armbar, for the fact that if you miss an armbar, you usually end up on the bottom.
Ken Shamrock, who was taught under catch philosophy, would be a good example to watch- for instance his fight with Alexander Otsuka where he grapevined his legs in the mount and inisisted on his keylock submission. Rickson Gracies matches with Takada would show him going for armbars and such.
4:
Catch was also not very adept at chokeholds. I can somewhat remember what Shamrock was saying about it- something along the lines of chokes are sometimes more difficult to see by the audience than joint locks (and catch in the form of Pancrase was intended to be entertainment). BJJ approached this from a strictly self defense point of view, and natrually the addition of a gi to the style meant a much greater variety of choke holds were available (if you ever wondered why it appeared as if Ken didnt do a great job of defending his neck in UFC 1, now you know)
5:
Consider the pain compliance moves you’re referring to- catch wrestling had its peak in the US with traveling canivals which would offer money- “pin our wrestler” Natrually, there were discrepancies over what was and wasnt a pin, and whether the pin was held long enough. These matches eventually changed to “make our wrestler give up” which is when you were able to throw all these submissions in there. This of course is hypothetical from my point of view, but a pain compliance move would most likely be a safer option than say a joint lock which breaks your opponents joints- if people were too scared to go against your wrestler, no one would fight him- if no one fights him, he doesnt make you any money.
Nowadays submission wrestling has incorporated so many styles into it that you rarely see anyone from a pure style anymore. This years recent Abu Dhabi showcased many BJJ fighters attacking with great footlock combinations, which was previously seen as their weakness. With the all the techniques and teachers out there, everything is coming together as one.